This invention relates to garments which prevent particulate matter from passing from the body of the wearer into the surrounding atmosphere and vice versa.
Conventional particulate control garments generally do not totally enclose the wearer and particulates can escape through openings in the fabric or gaps in the garment. Such garments are not usually complete systems with regard to particulate release, and this is a prime consideration in both clean room and contaminated environments. Although the garment fabric itself may release few particles, the movements of the wearer inside the garment has caused particulate-laden air to exhaust from inside the garment into the clean room atmosphere through gaps in the garment such as the openings at wrists, neck, ankles, waist or place of entry by the wearer. For example, it has been shown that even if the only opening is a high quality zip fastener, the wearer being otherwise encased in an impractical plastic bag, then particulate-laden air will continue to be discharged through the teeth and ends of the zip fastener whenever the wearer moves. Problems also arise when the conventional garment is manufactured of porous materials to allow a degree of comfort to the wearer. However, porous openings in the fabric often allow particles to escape and contaminate the environment and vice versa.
The nominal pore size of standard particulate control garments can be determined by the bubble point method (ASTM No. F316-80) or microscopic examination to be between about 6 and 66 microns (Chart 1) and the average filtration efficiencies, calculated using a laser based spectrophotometer and a NaCl challenge aerosol, are between about 7.75 and 78.57% at 0.1 microns (Chart 2). Many conventional garment materials, especially face and head coverings, actually contribute directly to the particulate problem in a clean room due to linting and their tendency to tear, thus releasing particles.
There are few materials available which do not shed particles and still allow filtered air passage. This fact, coupled with the design deficiencies in most garments, has hindered the development of a truly effective particulate controlling garment. The lack of a total unitized system for particulate control has forced users to assemble a series of unrelated garments such as overalls, goggles, face masks, caps, and so on, into as complete a system as is desired to achieve the necessary degree of particulate control. Such an improvised system is common in both clean rooms and contaminated environments, and is often both inefficient, untidy and uncomfortable.